Fitting of a hearing aid to a particular person's hearing impairment generally requires knowledge of clinically measured hearing thresholds for the person in question. The auditory brainstem response (ABR) can be used as an objective estimate of audiometric hearing thresholds (e.g. [Stürzebecher et al., 2006]). ABR signals are traditionally measured by surface electrodes mounted on the head with one electrode at the vertex or in the middle of the forehead, one behind the ear on the mastoid or on the earlobe, and one ground electrode on the opposite side of the head. Future hearing aids may, however, include electrodes on the surface of the hearing aid shell facing the ear canal to record electric brain wave signals such as an electroencephalogram (EEG) (cf. e.g. [Lunner, 2010]).
A portable EEG monitoring apparatus is described in [Kidmose and Westermann, 2010]. A hearing aid comprising electrodes for detecting electrical signals such as brain waves is described in [Kidmose and Mandic, 2011]. The design of stimuli for a system for the recording of an auditory brainstem response (ABR) of a person is e.g. described in WO 2006/003172 A1.
EP1073314A1 deals with a method of fitting a hearing aid. The method involves detecting auditory, involuntary body signals from the wearer of the hearing aid using a measuring device connected to the wearer. An evaluation device generates starting parameters for the hearing aid based on the measured values. These parameters are transferred to the signal processing unit of the hearing aid for individual adjustments. A signal may be fed to at least one ear of the wearer of the hearing aid. The measuring device detects the involuntary body signals caused by this signal. The signal may be acoustic, electrical, electromagnetic or mechanical.
The present disclosure builds further on the idea of using auditory models to continuously be able to present an auditory ‘test signal’ that does not disturb the user of the hearing aid, as described in EP2581038A1. A large part of the description and drawings of the present disclosure is taken from EP2581038A1 and presented here in identical or slightly modified form.